Vibrating plate

ABSTRACT

The invention relates to a vibrating plate ( 1 ), with a baseplate ( 2 ), set in vibration by means of a driving device ( 9 ), with at least one bottom plate ( 3 ), an upper plate ( 4 ) and a cell structure ( 5 ), arranged between the bottom plate ( 3 ) and the upper plate ( 4 ) to reinforce the base plate ( 2 ), as support components. According to the invention, the support components form a baseplate ( 2 ) with a natural resonance frequency 2 to 5 times, preferably 3 to 4 times the frequency of the vibration thereof. The support components ( 3, 4, 5, 8 ) are thus welded together to form a self-supporting body, such as to give a particularly stiff and light baseplate ( 2 ). As a result of the above properties, said vibrating plate ( 1 ) is particularly suitable for compacting uniform sands and snow, for example in the preparation of ski pistes.

The present invention relates to a vibration plate according to thepreamble of Claim 1 having a baseplate which may be set into vibrationsby an exciter device. Typically, a baseplate of this type has a groundplate whose bottom vibrates flatly on the material to be compressed.Because of the high dynamic load, most baseplates are manufactured frommassive thick steel plates, which are stabilized further via welded-onsupports if necessary.

A soil compression plate, in which the baseplate is implemented as aribbed hollow plastic part which is filled with sand or water beforeuse, is known from DE 4307993 C2. This plastic baseplate to be ballastedis to produce less noise during soil compression and allow morefavorable manufacturing. Specifically, the ribs extend from an uppercover plate to the ground plate and are particularly implemented as anopen-cell honeycomb structure. The honeycomb structure is used in thiscase to elevate the mechanical strength of the plastic component, andthe open-cell structure allows water or sand to be poured in anddistributed to ballast the baseplate.

These known vibration plates have been used successfully in manyapplications for soil compression. However, it has been shown that ifthe typical plates are used, among other things, grain refining throughgrain fractures and abrasion occur when compressing uniform and closelygraduated sands. It is disadvantageous in this case that grain refiningas a result of the mechanical action during installation alters thesoil-mechanical properties of the mixture, e.g., permeability, frostsensitivity, and compression features.

The quiet running of the known vibration plates is also problematic.Thus, in the event of increasing compression of the subsoil, irregularoscillations and tilting motions of the typical vibration plates mayoccur.

The present invention is therefore based on the object of providing avibration plate having a baseplate which may be set into vibrations byan exciter device, during whose use strong grain refining no longeroccurs and whose quiet running is simultaneously improved.

This object is achieved by a vibration plate according to Claim 1 and abaseplate according to Claim 22. Advantageous refinements are describedin the subclaims.

The vibration plate according to the present invention has a baseplate,which may be set into vibration by an exciter device, having at leastone ground plate, one top plate, and a cell structure positioned betweenthe ground plate and top plate, which stiffens the baseplate, assupporting components, the supporting components forming a baseplatehaving a stiffness in which the lowest natural frequency of thebaseplate is at least 2 to 5 times, preferably at least 3 to 4 times thefrequency of its vibration.

In this novel vibration plate, the supporting components are thusconnected to one another in such a way that they form a body having veryspecific vibration properties. The running properties of a vibrationplate always improve significantly if the supporting components at leaststiffen the ground plate in such a way that the lowest natural frequencyof the baseplate lies in the above-mentioned ranges of the frequency ofits vibrations during soil compression. In principle, a high stiffnessat low weight generates high natural frequencies, the lowest naturalfrequency from the bandwidth of the natural frequencies of the groundplate to reach a minimum value here. Such a baseplate vibratesharmonically in the event of increasing compression of the subsoilbefore it passes over to irregular and undesired tumbling or tiltingmotions.

In contrast to DE '993, for this purpose the baseplate must beespecially light precisely during the compression. For this purpose,supporting components known per se are used for stiffening and forlightweight construction in a way known from aircraft construction. Anespecially stiff and nonetheless light baseplate thus arises, which hasthe natural frequency values according to the present invention.

In particular, the cell structure is employed for the purpose of using asignificantly thinner ground plate or top plate than previously.According to the present invention, this construction allows the use of4 to 8 mm thick sheet steel plates, which results in a significantweight savings in relation to the known vibration plates made of steel.

The vibration plate according to the present invention therefore has asignificantly lower vibrating mass. This has the advantage that thenecessary amplitude for ensuring sufficient compression may be generatedusing lower centrifugal forces. Therefore, lower unbalance masses may beused, which may in turn be driven using a lower power. The undesiredgrain refining may thus be reduced and the exciter device maysimultaneously be operated more cost-effectively.

The significant weight reduction also allows the use of the vibrationplate for compressing debris in general. In this context, debris isunderstood as a loose stratification structure, formed from more or lessunequally large and loosely arrayed individual grains, having large porespaces. Through compression, this loose stratification structure may beconverted into a pore-filling graduated, dense stratification structurewhich is low in cavities. In this case, the grains may be sand or pebblegrains or even snow and ice crystals, for example. The vibration plateaccording to the present invention may thus also be used in the care andpreparation of ski pistes, cross-country skiing courses, or ski jumps toachieve longer service lives, without the plate sinking into the snow.This field of use is not accessible to the typical vibration platesbecause of the massive or ballasted implementation of the ground platesand the high weights resulting therefrom.

The vibration excitation of the baseplate is performed in this case withthe aid of an exciter device. This may be a rotary exciter or directedoscillator mounted on or even in the baseplate, for example. In thiscontext, excitation through an individual exciter or even throughmultiple hydraulically or mechanically synchronized exciters is alsoconceivable. Continuous shafts having one or more exciter weights arealternatively also usable as rotary exciters or directed oscillators.Eccentrically mounted shafts may also be used here.

In a preferred refinement of the present invention, the supportingcomponents are welded to one another to form a self-supporting body.Through the welding of the ground plate to the cell structure and thetop plate, an extraordinarily stiff body having further improvedvibration properties arises, which may be handled easily even duringproduction.

This light construction also allows a significantly wider execution ofthe plates running orthogonally to the operating direction. Thus,baseplates made of thin, high-strength steel having widths ofapproximately 2.25 m and a contact area of approximately 10,000 cm² maybe executed, which result in a total weight of the vibration plate ofbelow 400 kg. The corresponding surface pressure of such a vibrationplate is then only 0.4 N/cm² instead of the typical 5 N/cm². Inprinciple, it is advantageous if the surface pressure of the vibrationplate because of its intrinsic weight is between 0.1 N/cm² and 3 N/cm².In this case, the intrinsic weight of the vibration plate is to beunderstood as the total weight of the vibration plate when it is readyfor use. This includes, among other things, the weight of the baseplateand the weight of the exciter device, including the weight of possiblyexisting drives and/or suspension devices of the vibration plate. Inthis case, the surface pressure as a result of intrinsic weight is theweight force resulting from the intrinsic weight which the vibrationplate exerts on the flat soil surface it contacts.

According to the present invention, the vibration of the baseplate maybe set as desired at a frequency between 30 Hz and 60 Hz. Thus, thefrequency of 30 Hz may be adjusted up to larger frequency valuescontinuously, in steps, or fixed in one step. This frequency adjustmentis particularly necessary when compressing debris, sand being compressedat approximately 60 Hz.

In a further embodiment, the vibration of the baseplate may be set asdesired at an amplitude of more than 0.1 mm and less than 10 mm,preferably 5 mm. The amplitude may also be set from a value of 0.1 mm upto larger amplitude values continuously, in steps, or fixed in one step.

In a refinement, the baseplate is reinforced in that it has at least onelongitudinal girder welded to the cell structure as a further supportingcomponent. This girder extends parallel and over a significant part of along side of the baseplate. For this purpose, the long side of thebaseplate is understood as the longest side of the baseplate. It isessential in this embodiment that the longitudinal girder decisivelyreinforces the baseplate in regard to its flexural and torsionalstrength. In addition, the cell structure welded thereto is also heldbetter by the girder, which in turn further elevates the overallstiffness of the baseplate. Especially suitable girders are manufacturedfrom closed annular or box-type hollow profiles.

It is expedient if the longitudinal girder is positioned below theexciter device. Thus, the baseplate is additionally stiffenedparticularly in the highly loaded region below the exciter device andthe possibility is simultaneously provided of attaching the exciterdevice to the baseplate in a simple way, using screws, welding, orrivets, for example.

In order to further increase the overall stiffness of the vibrationplate and particularly the baseplate, the longitudinal girder isimplemented as a frame lying on the ground plate. A significantlyincreased spatial stiffness of the longitudinal girder itself thusresults, which may be increased even further if the stiffening cellstructure is welded into the intermediate space enclosed by the frame.In addition, as already described above, the cell structure is alsowelded around the frame. This embodiment of the support allows arelatively wide exciter device to be attached to the vibration plate.

In an especially preferred refinement, the individual cells of the cellstructure each have a base whose maximum lateral extension is 20 mm to200 mm, preferably 56 mm to 162 mm. This very fine-celled cell structureallows the ground plate in particular to be implemented as very thin,because of the narrow support interval of the cell walls, without strongbuckling of this baseplate, which is only 4 mm to 8 mm thick, resulting.

The cell structure typically has at least partially closed cells havingpolygonal bases. The execution of the cell structure from partiallyclosed cells results in further stiffening. The execution usingdifferent polygonal bases has the advantage that the cell structure mayeven be tailored to more complicated geometries of the outline of theground plate. Triangular, rectangular, pentagonal, or hexagonal andpolygonal regular or even irregular shapes are advantageous.

In a preferred embodiment, the cell structure has cells having at leastpartially round bases. It is thus possible to provide even rounded basesof the ground plate with a cell structure. It is also advantageous tomanufacture the cell structure from tubes, individual tube sectionssimply being joined to one another. For this purpose, circularcylindrical tubes may be used, for example.

In an advantageous refinement, the cell structure at least partially hasdifferent cell shapes. This has the advantage that the stiffening effectof the cell structure may be varied distributed over the ground plate.This may be performed to adapt the stiffness to the load situation.Thus, a cell structure having especially many small cells would be usedin regions having an especially large load, e.g., at the edge of theground plate or in the region of the vibration excitation. Morecomplicated geometries of the baseplate may also be manufactured usingdifferent cell shapes. Thus, for example, the cell structure may betailored to a drop-shaped cross-section of the baseplate.

The cell structure preferably has closed cell side walls. A highstiffness and strength of the cell structure in the particular cell wallplanes thus results. This simultaneously allows continuous welding ofthe cell structure with adjoining supporting components such as theground plate, the top plate, or the longitudinal girder. The weld seamsare longer than in an open-cell construction, in which the cell wallshave recesses in the wall base regions. This increases the strength andallows thinner cell walls to be used. At the same time, the walls of thelongitudinal girder or the lateral plates of the baseplate, whichterminate the cross-section, may also be used as cell walls.

In order to achieve good and uniform load dissipation and producibilityof the cells, they are designed in such a way that planes of the cellsparallel to the base each have the same shape and area as the base. Inconcrete form, this means that rectangular cells, for example, may haveside walls positioned at an oblique angle to the base, for example, butdiametrically opposing cell side walls run parallel to one another. Thecells are preferably shaped so that the cell side walls are essentiallyloaded by perpendicular forces. For this purpose, the cell side wallsare best positioned perpendicularly to the supporting ground plateand/or top plate and run linearly away therefrom.

It is not always necessary to support the top plate by the cellstructure precisely like the ground plate, e.g., if the cell structureis only used to reinforce the ground plate in some regions. It is thenadvantageous not to lead the cell structure from the ground plate up tothe top plate and thus achieve a further weight reduction. In such acase, the cell structure is expediently open on top.

The cell structure is preferably partially closed on top by the topplate. This only partial covering typically occurs if other componentsof the vibration plate cover the cell structure on top. In any case,however, the cell structure is to be protected by other covers frompenetration of material to be compressed, if necessary.

Independently of this, if the top plate is solidly connected to the cellstructure, it results in further stiffening of the baseplate. The cellstructure is also covered on top so that no material to be compressedmay collect in the cell structure. The weight of the vibration plateand/or the baseplate thus remains constant even in the event of longuse. Weight changes due to accumulations of the material to becompressed thus may not lead to a change of the vibration properties ofthe vibration plate. Furthermore, the top plate makes cleaning of thevibration plate easier. A removable top plate is also advantageous.

In another refinement, the bottom of the ground plate is at leastpartially provided with a wear protector. This has the advantage thatthe ground plate, which is implemented as very thin because of thedesired weight reduction, is not worn or damaged due to friction withthe material to be compressed. Such a wear protector may be a coatingmade of a suitable plastic which is glued onto the ground plate or evena plastic or metal plate clamped onto the ground plate, which is easy toreplace. The wear protector may be attached to the baseplate throughscrews, rivets, or clamps, for example.

In a further embodiment, profiled strips are attached externally to theground plate. This leads to further stiffening of the baseplate and, inaddition, to profiling of the subsoil. For this purpose, differentprofiles, such as trapezoids, triangles, or even wavy profiles, areusable. They may also be attached to the ground plate through screws,rivets, clamps, or gluing, for example.

In principle, the vibration plate may be self-driven and provided with ahandle so that it may be pushed or pulled vibrating over the soil by aperson in a generally known way. One then refers to a self-drivenvibration plate. In an advantageous embodiment, however, the vibrationplate has a vibration-insulated suspension for installation on aself-propelled support device, which is connected to one of thesupporting components of the baseplate. It is then a non-self-propelledvibration plate. The suspension is best connected to the longitudinalgirder or via the cell structure to the baseplate. Through the directconnection to the cell structure, it is possible to dispense with afurther fastener. The vibration insulation of the suspension may beproduced in this case, for example, via rubber or even spring-damperelements and results in the vibrations of the vibration plate not beingtransmitted to the self-propelled support device. Such a self-propelledsupport device may be a tractor, a snowcat, a street constructionvehicle, or even a rolling mill drive for soil processing, for example.

In a further embodiment of the present invention, the exciter device isattached to at least one of the supporting components of the baseplate.Typically and especially expediently, the exciter device is attached tothe longitudinal girder, as described above. However, embodiments inwhich the exciter device is attached directly to a possibly speciallyreinforced cell structure are also expedient.

Normally, a separate drive is provided for the exciter device, e.g., agasoline engine on the vibration plate. In the event of an especiallylight vibration plate, however, a drive of the exciter device positionedon the vibration plate is dispensed with. Instead of this, the exciterdevice may be coupled to a drive of the self-propelled support deviceand driven thereby. The exciter device is then driven in a typical wayby a hydraulic or even mechanical drive. For this purpose, the exciterdevice has couplings for hydraulic lines or a driveshaft, for example,which may be connected to the corresponding counter couplings of theself-propelled support device.

It is especially advantageous if the baseplate has an operating widthessentially corresponding to its long side, which is at leastapproximately as wide as the self-propelled support device. Inparticular, the operating width is to be wider than the lane of thesupport device. The vibration plate thus smoothes the lanes left behindby the support device when the vibration plate is pulled behind theself-propelled support device. For this purpose, the vibration plate isaligned with its long side perpendicular to the travel direction. Alongthe operating width, the vibration plate has a compressing effect on thematerial lying underneath it. Because of the especially wide embodiment,an especially effective mode of operation of the vibration plateresults.

A vibration plate whose baseplate has a cross-section in which theregion of the ground plate lying forward in the operating direction iscurved upward together with a forward region of the top plate isespecially well suitable for debris compression. The upward bend of theground plate lying forward in the operating direction prevents the platefrom digging into the material to be compressed. Because the top plateis also bent upward, a cell structure may be positioned between the twoplates. This provides the two very thin plates, which are bent upward,with good spatial stability.

So that parts of the material to be compressed possibly arriving on thevibration plate do not collect there, the baseplate (2) preferably has across-section in which the region of the top plate lying to the rear inthe operating direction is slanted falling downward toward the groundplate. Thus, for example, snow or sand residues simply slide off fromthe surface of the baseplate to the rear.

In the following, the present invention will be explained further on thebasis of an exemplary embodiment illustrated in the drawing.

FIG. 1 schematically shows the section A-A through a vibration platereinforced with a cell structure;

FIG. 2 schematically shows the top view of a part of the vibration plateshown in FIG. 1 with the internal cell structure illustrated;

FIG. 3 schematically shows the detail illustration of the section B-B ofthe vibration plate shown in FIG. 1 and FIG. 2;

FIG. 4 shows a cell structure having a rectangular base; and

FIG. 5 shows a cell structure having a triangular base.

In detail, FIG. 1 shows the section A-A through vibration plate 1 forcompressing and smoothing ski pistes. It contains a baseplate 2, whichis stiffened using a cell structure 5, an exciter device 9 forgenerating vibrations, and a device support 10, which is attached to aself-propelled support device.

In the embodiment shown here, the baseplate 2 contains a ground plate 3,a top plate 4, an interposed cell structure 5, and a longitudinal girder8, which are all made of steel, as supporting components. The exciterdevice 9 is attached to the frame-shaped longitudinal girder 8, which isin turn welded to the ground plate 3. The longitudinal girder 8 runsover the entire long side of the baseplate 2 in this case.

In this embodiment, the cell structure 5 comprises continuous andvertically running cell long walls 6 and cell transverse walls 7,positioned perpendicularly to one another, which are welded permanentlyto the baseplate 2 and the top plate 4 here. The cell walls have a wallinterval from 50 mm to 150 mm in this case and have no openings.Therefore, this is a closed-cell cell structure having hollow cellswhich are cuboid in the central region of the baseplate. In the regionenclosed by the frame-shaped longitudinal girder 8 and along the sideplates 14, the cell walls 6, 7 are positioned more closely, since thisregion is loaded especially strongly by the exciter wave device. Thecell structure 5 welded to the girder 8 simultaneously stabilizes thegirder 8, and thus forms, together with the ground and top plates whichare also welded on, a light, self-supporting body having high torsionaland flexural strength.

In this embodiment, the baseplate 2 is curved upward on the side lyingforward in the operating direction, in order to push snow which collectsin front of the vibration plate under the vibration plate and slide wellover wavy ground. In order to support the 4 mm thick top plate andequally thick ground plate, both plates are curved upward and theinterior lying between them is reinforced using the cell structure 5made of 3 mm thick sheet steel. The ground plate 3 and the top plate 4run toward one another to a point, a crimp 15 of the ground plate 3forming the tip of the baseplate 2 and simultaneously a support for thetop plate 4. In the rear region of the baseplate, the top plate 4 dropstoward the ground plate 3, a very narrow crimp 16 of the ground plate 3forming a rear support for the top plate 4.

The ground plate 3 is provided on the bottom with a wear protector 12made of abrasion-resistant plastic. This is screwed onto the groundplate 3 and prevents damage to the ground plate 3 from sharp stoneswhich project out of the snow, for example. On the rear end of theground plate 3, a profiled strip 13, which is mounted transversely tothe travel direction over the entire width, is located below the groundplate 3. This strip is also attached replaceably and is used for furtherstiffening of the end section of the baseplate 2 and also for profilingthe compressed snow and stabilizing the position of the vibration plateas it slides over the snow.

The vibration plate 1 is suspended on a self-propelled support devicewhich travels in front, such as a snowcat in this case, and is pulledover the snow by this device. The device support 10 of the snowcat isused for suspension. This is attached to the vibration-insulatedsuspension 11 of the vibration plate 1 without performing modificationson the support device. The vibration plate 1 has no separate drive ofthe exciter device 9. Instead of this, the exciter device 9 has a shaft18 provided with a coupling 17, using which the exciter device may becoupled to a drive of the snowcat and then driven thereby. A hydraulichose 19 having coupling 20 is used to connect the exciter device 9 tothe hydraulic system of the snowcat.

The variation of the cell structure 5 in size, shape, andcross-sectional dimensions may be recognized from the top viewillustrated in FIG. 2 of a part of the vibration plate illustrated inFIG. 1. Thus, in the region below the exciter device 9, the cell longwalls 6 and also the cell transverse walls are positioned more closelyto one another. The edge of the baseplate 2 is also provided with moreclosely positioned cell transverse walls 7. The remaining regions of thecell structure 5 have cells which are formed from thinner cell longwalls 6 and in which the support walls 8 and/or the ground plate 3,which are curved up at the front and rear, form the cell transversewalls 7.

The cell structure 5 is delimited in this case at the lateral edges ofthe vibration plate 1 by side walls 14, as may be seen in the sectionB-B shown in FIG. 3. The profiled strip 13 is a trapezoidal profile forproducing a furrowed piste surface in this embodiment. Thevibration-insulated suspension elements 11 are positioned between themultipart exciter devices 9 and connected directly to the cell structure5 in this exemplary embodiment.

FIGS. 4 and 5, two details from two different cell structures 5 areshown, the cell shown in FIG. 4 having a rectangular and perpendicularbase and that in FIG. 5 having a triangular base. The maximum lateralextension 22 of the base 23 enclosed by the cell walls 6 and 7corresponds in FIG. 4 to the external lateral interval of thediametrically opposing cell side walls 6 spaced farthest apart. In FIG.5, the maximum lateral extension 22 of the base 23 is the externallateral length 22 of the third and longest cell wall 21, which runsdiagonally here. In the example of the cell shown in FIG. 4, this meansconcretely, at a cell wall thickness of 3 mm and an open wall intervalof the two diametrically opposite cell side walls 6 of 50 mm, that themaximum lateral extension 22 of the cell has a value of 56 mm. In atubular cell having a circular base (not shown here), the maximumlateral extension thus corresponds to the internal diameter plus twicethe wall thickness of the cell wall.

1. A vibration plate, having a baseplate, which may be set intovibration by an exciter device, having at least one ground plate, a topplate, and a cell structure, which is positioned between the groundplate and the top plate and stiffens the baseplate, as supportingcomponents, wherein the supporting components form a baseplate having astiffness in which the lowest natural frequency of the baseplate is atleast 2 to 5 times, preferably at least 3 to 4 times the frequency ofits vibration.
 2. The vibration plate according to claim 1, wherein thesupporting components are welded to one another to form aself-supporting body.
 3. The vibration plate according to claim 1,wherein the vibration plate has a surface pressure because of itsintrinsic weight between 0.1 N/cm² and 3 N/cm².
 4. The vibration plateaccording to claim 1 wherein the vibration of the baseplate may be setas desired at a frequency between 30 Hz and 60 Hz.
 5. The vibrationplate according to claim 1 wherein the vibration of the baseplate may beset as desired at an amplitude of more than 0.1 mm and less than 10 mm,preferably 5 mm.
 6. The vibration plate according to claim 1 wherein thebaseplate has at least one longitudinal girder welded to the cellstructure as a further supporting component, which extends parallel toand over a significant part of a long side of the baseplate.
 7. Thevibration plate according to claim 1 wherein the longitudinal girder ispositioned below the exciter device.
 8. The vibration plate according toclaim 1 wherein the longitudinal girder is implemented as a frame lyingon the ground plate.
 9. The vibration plate according to claim 1 whereinthe individual cells of the cell structure each have a base, whosemaximum lateral extension is 20 mm to 200 mm, preferably 56 mm to 162mm.
 10. The vibration plate according to claim 1 wherein the cellstructure has cells having at least partially round bases.
 11. Thevibration plate according to claim 1 wherein the cell structure has atleast partially differing cell shapes.
 12. The vibration plate accordingto claim 1 wherein the cell structure has closed cell side walls. 13.The vibration plate according to claim 1 wherein planes of the cellsparallel to the base each have the same shape and area as the base. 14.The vibration plate according to claim 1 wherein the cell structure isopen on top.
 15. The vibration plate according to claim 1 wherein thecell structure is partially closed on top by the top plate.
 16. Thevibration plate according to claim 1 wherein a profiled strip isattached externally to the ground plate.
 17. The vibration plateaccording to claim 1 wherein the vibration plate has avibration-insulated suspension for installation on a self-propelledsupport device, which is connected to one of the supporting componentsof the baseplate.
 18. The vibration plate according to claim 1 whereinthe exciter device is attached to at least one of the supportingcomponents of the baseplate.
 19. The vibration plate according to claim1 wherein the exciter device may be coupled to a drive of theself-propelled support device and driven thereby.
 20. The vibrationplate according to claim 1 wherein the baseplate has an operating widthessentially corresponding to its long side, which is at leastapproximately as wide as the self-propelled support device, particularlywider than the lane of the support device.
 21. The vibration plateaccording to to claim 1 wherein the baseplate has a cross-section, inwhich the region of the ground plate lying forward in operatingdirection is curved upward together with a forward region of the topplate.
 22. The vibration plate according to claim 1 wherein thebaseplate has a cross-section in which the region of the top plate lyingto the rear in the operating direction is slanted falling downwardtoward the ground plate.
 23. (canceled)